Ketones and ketoacids are alternative fuels for the body that are made when glucose is in short supply. They are made in the liver from the breakdown of fats.
Ketones are formed when there is not enough sugar or glucose to supply the body’s fuel needs. This occurs overnight, and during dieting or fasting. During these periods, insulin levels are low, but glucagon and epinephrine levels are relatively normal.
This combination of low insulin, and relatively normal glucagon and epinephrine levels causes fat to be released from the fat cells. The fats travel through the blood circulation to reach the liver where they are processed into ketone units.
The ketone units then circulate back into the blood stream and are picked up by the muscle and other tissues to fuel your body’s metabolism. In a person without diabetes, ketone production is the body’s normal adaptation to starvation.
Blood sugar levels never get too high, because the production is regulated by just the right balance of insulin, glucagon and other hormones.
The blood sugar level regulation mechanism
When you eat rice, bread, or any other typical food high in carbohydrates, it is digested by the stomach and small intestine, where it is absorbed into the blood as glucose:
The sugar in food is absorbed into the blood as glucose.
The pancreas secretes insulin in reaction to the increase in glucose.
Because the glucose is absorbed into the liver, muscle, adipose (fat) tissue and other cells, the blood sugar level drops to the level it was before anything was eaten.
This is the mechanism found in healthy people.